Propeller for aircraft



H. SUKOHL PR'OPELLER FOR AIRCRAFT Aug. 18, 1942.

Filed Aug. l5, 1939-` 17@ wwf r /1 ternally of the said straps whic Patented Aug. 18,1942

OFFICE y PROPELLER FOR AIRCRAFT Heinrich sukohl, Berlin-waiamannslust, Germany Application August 15, 1939, Serial No. A In Germany February 24, 1939 3 claims. (c1. 170;-159) My invention relates to'improvements in propellers for air craft, and the object of the im'- provements is to provide a propeller which has low weight and high strength. With this object in view my invention consists in building the propeller blade upon a root portion formed with a transverse shoulder, and wrapping straps of high tensile strength around said shoulder and extending therefrom over the whole or va large portion of the length of blade and xed thereto. In most cases a core or cores e provided incore or cores substantially have-the functionv to give the de-l sired shape tothe blade, while the said straps have the function to impart strength thereto and particularly to transmit the centrifugal force to. the root and to take up bending and torsional forces. Therefore the core is preferably made from light material such as balsa wood, artificial sponge like material, and the like.

For the purpose of explaining the invention and example embodying the same has been shown in lthe accompanying drawing in which the same reference charactershave been used in all the views to indicate corresponding parts. In said drawing,

Fig. 1 is an elevation of the blade of the propeller with some of the layers of straps removed,

Fig. 2 is a sectional elevation taken on the line 2-2 of Fig. 1,

Fig. 3 is a sectional plan view taken on the line 3-3 of Fig. 1,

Fig. 4 is an elevation showing the root of the blade, and 'e 3 and showing a modification. In the construction shown inthe drawing the propeller consists of a root comprising a cylindrical stem portion I adapted at its inner end to be fixed to the hub of the propeller, and at its outer end widened in a flat outwardly tapering portion 2 projecting laterally beyond the portion I to provide at the inner edge transverse shoulders 9, a core comprising a portion 3 fixed to the tapering portion 2l of the root and made from Fig..5 is a sectional plan view similar to Fig.l

wood, and a portion 4 made from light materialy such as balsa Wood and flxed to the portion 3, and straps preferably made from wood veneer of high tensile strength wrapped upon the transverse shoulders 9 of the root and extending thence longitudinally of the blade.v The portions 2, 3 and 4 are preferably united by glueing. or vother- WiSe, and the parts 2. and 3 are further held to- 4 scribed. The root I, 2 may be made from metal,

gether by additional strapsY as will now be de- .end of the propeller blade.

hard wood, or reinforced artificial resins;

Around the part of the core portion 3 fixed to the portion 2 of the root straps 5 of wood veneer are Wound transversely in one or more layers according to the desired strength. The said Y'straps may be of relatively great length, wound spirally around the union of core 3 with 'the portion 2 of the root, as is and 4, `or they may consist of relatively short pieces, each wound once around the core with the ends overlapping, as is shown in Fig. 5, in which latter case the overlapping ends of adjacent and superposed windings are preferably displaced with relation to one another. The object of the additional straps 5 is to fix the core 3 to the portion 2 ofthe root. Y

Around the laterally projecting shoulders- 9 several'plies of straps 6 are wound. One end of each strap preferably extends from a line slightly beyond v.the outer end of the portion 2, indicated by the dotted line 'I in Fig. 1.

the :straps extend towards the root;-they are and they extend thence outwardly to the' outer Preferably the shoulders 9 of the portion 2 are short ends 6 of the-straps are disposed axially of the `blade the longer ends thereof are disposed at a suitable angle to the axis, and'so that the' r portions of the straps coming from opposite sides In Fig. 1 some of the plies of straps have been broken away. In the left hand part of the ligure I have shown in full lines the longends of the straps 6 extending from the root'to the outer end of the blade, while the ends B are shown in l dottedlines. 0n the right hand side'the lateral plies of straps 6 have been partly broken away in order to 'show also portions 6' of another ply of straps.

As has been stated above the coresubstantially uhas the function to give the desired shape to the blade, and therefore it may have a shape and size dinerent from that-shown in the figures,

shown in Figs. 1

From the line I disposed at suoliA angles to the axis of the blade, that whenl the.

the inner transverse plies 54 and longitudinally of the veneer and in some cases the core may be entirely omitted, the blade consisting exclusively of the root and the straps wound upon the same. That is to say, the blade consists of a body and tension straps, the body includes" a root member and it may include a core also. lThe core, however, is not essential and the root member may constitute the complete body without it.

The straps are made from a material of high tensile strength. They may be made from metal, but I prefer to make them from wood veneer in which the grain runs longitudinally of the straps, so that the high tensile strength is made use of.

In the figures I have shown only one ply of longitudinal strap 6, 6 and one ply of transverse straps 5. But it will be understood that a suitable number of plies is provided, in accordance with the desired tensile strength depending on the centrifugal force.

I claim:

1. A blade for propellers 'for air craft, comprising a root having a flat tapering portion and shaped to provide a transverse shoulder, a core engaging the opposite sides of said flat tapering portion, a strap of high tensile strength wrapped transversely around the portion of the cr re engaging said tapering portion of the root, and a plurality of straps of high tensile strength wrapped around said shoulder and extending longitudinally of the blade.

2. A propeller blade including a root adapted to be fixed at its inner end to a hub and having at its outer end a widened outwardly tapering portion with transverse shoulders at the inner edge, a core secured to the outwardly tapering portion of the root, and tension straps wrapped upon the said shoulders of the widened outwardly tapering portion of the root and overlying the opposite faces of the core.

3. A propeller blade that includes a body and tension straps laid thereon, the body including a root that comprises a stem adapted at 4its inner end to be secured to a hub and at its outer end widened in a flat outwardly tapering portion with transverse shoulders at the inner edge, the tension straps being wrapped upon said shoulders and extending thence outwardly upon the body.

HEINRICH SUKOHL. 

